Power packs are often used to power mobile devices, such as cellular telephones, personal digital assistants (PDAs), media players and the like. Typically, power packs include rechargeable electrochemical cells or batteries, which are charged using a dedicated charger unit drawing power from some power source such as the mains or a vehicle battery and which may be external or internal to the device.
Charger units powered from mains or power lines usually consist of a bulky plug box, containing a step-down transformer and a rectifier, with conducting pins for connecting to the mains socket. When in use, the plug box is plugged into a mains socket and a trailing cord connects to the device via a connecting plug. If the trailing wire is snagged or jerked the wire and connectors may be damaged or the device may be pulled to the ground. Moreover, the trailing wire itself is inconvenient and unsightly particularly where a number of devices are charged from a common power socket and the trailing wires may become entangled. Thus wireless power charging is desirable